Could the new full-body airport security scans expose you to dangerous amounts of radiation? Some scientists say there’s reason to worry. Here’s what you need to know about this hot-button topic...

As the Thanksgiving travel season moved into full swing this week, many airline passengers got their first experience of the Transportation Security Administration’s new security measures – scanners that display an image of their nude figure.

These scanners, which are currently installed at about 70 large and midsize airports, have caused an uproar.

While some fliers are upset about the loss of privacy these X-ray images represent, others worry about being exposed to radiation when passing through security.

The health concerns are backed by some scientists, who say the scanners could potentially raise our cancer risk, especially for frequent fliers, pilots and flight attendants.

“In the radiation world, we all subscribe to the doctrine of ALARA – As Low As Reasonably Achievable,” says biophysicist David Brenner, Ph.D., head of Columbia University’s Center for Radiological Research in New York City. “We know the radiation dose is very low, but there are different views of just how low.”

Are these machines really dangerous? And how does the radiation risk compare to medical X-rays? We asked the experts.

How Scanners WorkThere are two kinds of full-body imaging devices currently in use at various airports. They both create an image of the body and any potential hidden objects.

Backscatter scanners work by shooting low-density X-rays that barely penetrate the clothes, then measuring what bounces back.

Millimeter-wave (mmw) machines emit beams of radio-frequency energy that pass through the clothes and bounce off surfaces underneath.

Of the two, backscatter radiation is considered more dangerous. That’s because it’s ionizing, meaning the X-ray has enough energy to strip away electrons from atoms or break some chemical bonds, leading to an increased risk of cancer.

But it’s the amount - not the kind - of radiation, that’s important. The levels emitted by backscatter machines are “minuscule,” according to a report just released by the Food and Drug Administration.

In fact, radiation from a backscatter scan is 100 times less than you’d get from a chest X-ray (about 8 to 10 millirems, the unit used to measure radiation), says James Hevezi, Ph.D., chair of the American College of Radiology’s Medical Physics Division.

Some researchers, however, are concerned that scanner malfunctions could increase exposure. In a 2010 journal article, Arizona State University physicists Peter Rez, Ph.D., and Kenneth Mossman, Ph.D., wrote that “serious consideration should be given to the possibility of unintended and unnecessary doses to passengers due to malfunctioning equipment.”

But they also say that, with normal use, “calculated doses are well below doses associated with health effects.”

Is a Little Still Too Much?Other scientists counter that the potential risk from radiation increases with every exposure, and even small amounts should be avoided whenever possible.

That’s why Brenner recommends that pregnant women and young children avoid the device.

And even tiny amounts lead to real risk when magnified over large populations, Brenner says.

“Suppose some activity involves a very, very small cancer risk, but a billion people are each exposed to [it],” he says. “Chances are that some of them would get cancer as a result, even though the individual risk is extremely small.”

That’s potentially the case with airport scanners, given that 700 million people travel through U.S. airports every year, Brenner says.

The risk could be higher still for frequent fliers, he adds.

When you multiply the risk by 200 or 300 commercial airline crew members or frequent fliers, “the estimated individual risks are still small, but perhaps no longer ‘miniscule,’” he says.

Pilots’ unions have echoed the concerns about the cumulative effects of multiple screenings, and some have urged their members to refuse being scanned.

Some scientists have expressed concern that even small doses of radiation can become more dangerous when concentrated in a particular area – in this case, the skin.

In fact, a group from the University of California at San Francisco sent a letter to the White House in April asking for an evaluation of the scanning devices by an impartial panel of experts.

“While the dose would be safe if it were distributed throughout the volume of the entire body, the dose to the skin may be dangerously high,” they wrote.

UCSF biochemist John Sedat, Ph.D., one of the participants, said it was difficult to gauge the actual risk because the device is classified, so scientists don’t know the beam intensity and other details.

More Radiation from Flying ItselfMany people don’t realize that flying itself exposes them to radiation, about 1,000 times the dose received from a backscatter scanner.

That’s because traveling above Earth’s protective atmosphere exposes you to higher levels of natural cosmic rays from outer space, the sun and other stars. The higher you fly, the greater the exposure. In fact, a single cross-country trip equals half the exposure of a routine chest X-ray.

Levels are higher during “solar flares,” bursts of electromagnetic radiation emanating from the sun’s atmosphere. But those are both brief and rare.

If you’re concerned about this extra exposure, check for solar-radiation alerts on the National Oceanic and Atmospheric Administration’s website.

Frequent flyers – those who log up to 85,000 miles per year – have as much exposure as the maximum recommended for radiation workers, according to Barish and Stephan Dilchert, Ph.D., a business management professor at New York’s Baruch College.

They’re calling for businesses to educate their frequent-traveling employees about radiation risks and have them keep track of their annual in-flight time, as well as offer regular health screenings for workers who fly a lot.

The Bottom LineDespite privacy and safety concerns, recent polls show that most Americans accept the full-body scans. And according to TSA chief John Pistole, they’re here to stay.

If you prefer not to go through a scanner – despite the relatively low radiation risk – you’ll probably receive an even more unpleasant full-body pat-down.

But the public outcry is having an effect. In a Nov. 21 interview on CNN, Pistole said the agency is working to make screening as “minimally invasive as possible,” adding that “there’s a continual process of refinement and adjustment to ensure that best practices are applied.”

If nothing else, you may no longer face the embarrassment of having your naked body displayed to a TSA screener.

In an interview with the online magazine Slate, an executive for scanner manufacturer Rapiscan said the company is working on software that will display only the image of a “plain, test-dummy-type body” while the machine flags any foreign objects.

Are You a Travel Pro?Even if you have decided to engage in a bit of last minute travel planning, remember that some essentials are too important to forget. Take this travel quiz to see if you are ready to set off on an adventure of your own!

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